blob: 14e16eac42cf1044d6d4b94ba00c0ce88162b93b [file] [log] [blame]
// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.
#include "base/metrics/field_trial.h"
#include "base/build_time.h"
#include "base/logging.h"
#include "base/metrics/histogram.h"
#include "base/rand_util.h"
#include "base/sha1.h"
#include "base/stringprintf.h"
#include "base/string_util.h"
#include "base/sys_byteorder.h"
#include "base/utf_string_conversions.h"
namespace base {
namespace {
// Created a time value based on |year|, |month| and |day_of_month| parameters.
Time CreateTimeFromParams(int year, int month, int day_of_month) {
DCHECK_GT(year, 1970);
DCHECK_GT(month, 0);
DCHECK_LT(month, 13);
DCHECK_GT(day_of_month, 0);
DCHECK_LT(day_of_month, 32);
Time::Exploded exploded;
exploded.year = year;
exploded.month = month;
exploded.day_of_week = 0; // Should be unused.
exploded.day_of_month = day_of_month;
exploded.hour = 0;
exploded.minute = 0;
exploded.second = 0;
exploded.millisecond = 0;
return Time::FromLocalExploded(exploded);
}
} // namespace
static const char kHistogramFieldTrialSeparator('_');
// statics
const int FieldTrial::kNotFinalized = -1;
const int FieldTrial::kDefaultGroupNumber = 0;
bool FieldTrial::enable_benchmarking_ = false;
const char FieldTrialList::kPersistentStringSeparator('/');
int FieldTrialList::kExpirationYearInFuture = 0;
//------------------------------------------------------------------------------
// FieldTrial methods and members.
FieldTrial::FieldTrial(const std::string& trial_name,
const Probability total_probability,
const std::string& default_group_name)
: trial_name_(trial_name),
divisor_(total_probability),
default_group_name_(default_group_name),
random_(static_cast<Probability>(divisor_ * RandDouble())),
accumulated_group_probability_(0),
next_group_number_(kDefaultGroupNumber + 1),
group_(kNotFinalized),
enable_field_trial_(true),
forced_(false),
group_reported_(false) {
DCHECK_GT(total_probability, 0);
DCHECK(!trial_name_.empty());
DCHECK(!default_group_name_.empty());
}
FieldTrial::EntropyProvider::~EntropyProvider() {
}
void FieldTrial::UseOneTimeRandomization() {
// No need to specify randomization when the group choice was forced.
if (forced_)
return;
DCHECK_EQ(group_, kNotFinalized);
DCHECK_EQ(kDefaultGroupNumber + 1, next_group_number_);
const EntropyProvider* entropy_provider =
FieldTrialList::GetEntropyProviderForOneTimeRandomization();
if (!entropy_provider) {
NOTREACHED();
// TODO(stevet): Remove this temporary histogram when logging
// investigations are complete.
UMA_HISTOGRAM_BOOLEAN("Variations.DisabledNoEntropyProvider", true);
Disable();
return;
}
random_ = static_cast<Probability>(
divisor_ * entropy_provider->GetEntropyForTrial(trial_name_));
}
void FieldTrial::Disable() {
DCHECK(!group_reported_);
enable_field_trial_ = false;
// In case we are disabled after initialization, we need to switch
// the trial to the default group.
if (group_ != kNotFinalized) {
// Only reset when not already the default group, because in case we were
// forced to the default group, the group number may not be
// kDefaultGroupNumber, so we should keep it as is.
if (group_name_ != default_group_name_)
SetGroupChoice(default_group_name_, kDefaultGroupNumber);
}
}
int FieldTrial::AppendGroup(const std::string& name,
Probability group_probability) {
// When the group choice was previously forced, we only need to return the
// the id of the chosen group, and anything can be returned for the others.
if (forced_) {
DCHECK(!group_name_.empty());
if (name == group_name_) {
return group_;
}
DCHECK_NE(next_group_number_, group_);
// We still return different numbers each time, in case some caller need
// them to be different.
return next_group_number_++;
}
DCHECK_LE(group_probability, divisor_);
DCHECK_GE(group_probability, 0);
if (enable_benchmarking_ || !enable_field_trial_)
group_probability = 0;
accumulated_group_probability_ += group_probability;
DCHECK_LE(accumulated_group_probability_, divisor_);
if (group_ == kNotFinalized && accumulated_group_probability_ > random_) {
// This is the group that crossed the random line, so we do the assignment.
SetGroupChoice(name, next_group_number_);
}
return next_group_number_++;
}
int FieldTrial::group() {
FinalizeGroupChoice();
FieldTrialList::NotifyFieldTrialGroupSelection(this);
return group_;
}
const std::string& FieldTrial::group_name() {
// Call |group()| to ensure group gets assigned and observers are notified.
group();
DCHECK(!group_name_.empty());
return group_name_;
}
// static
std::string FieldTrial::MakeName(const std::string& name_prefix,
const std::string& trial_name) {
std::string big_string(name_prefix);
big_string.append(1, kHistogramFieldTrialSeparator);
return big_string.append(FieldTrialList::FindFullName(trial_name));
}
// static
void FieldTrial::EnableBenchmarking() {
DCHECK_EQ(0u, FieldTrialList::GetFieldTrialCount());
enable_benchmarking_ = true;
}
void FieldTrial::SetForced() {
// We might have been forced before (e.g., by CreateFieldTrial) and it's
// first come first served, e.g., command line switch has precedence.
if (forced_)
return;
// And we must finalize the group choice before we mark ourselves as forced.
FinalizeGroupChoice();
forced_ = true;
}
FieldTrial::~FieldTrial() {}
void FieldTrial::SetGroupChoice(const std::string& group_name, int number) {
group_ = number;
if (group_name.empty())
StringAppendF(&group_name_, "%d", group_);
else
group_name_ = group_name;
DVLOG(1) << "Field trial: " << trial_name_ << " Group choice:" << group_name_;
}
void FieldTrial::FinalizeGroupChoice() {
if (group_ != kNotFinalized)
return;
accumulated_group_probability_ = divisor_;
// Here it's OK to use |kDefaultGroupNumber| since we can't be forced and not
// finalized.
DCHECK(!forced_);
SetGroupChoice(default_group_name_, kDefaultGroupNumber);
}
bool FieldTrial::GetActiveGroup(ActiveGroup* active_group) const {
if (!group_reported_ || !enable_field_trial_) {
// TODO(asvitkine): Temporary histogram. Remove this once it is not needed.
if (trial_name_ == "UMA-Uniformity-Trial-1-Percent") {
const int kGroupNotReported = 1;
const int kTrialDisabled = 2;
int value = 0;
if (!group_reported_)
value |= kGroupNotReported;
if (!enable_field_trial_)
value |= kTrialDisabled;
UMA_HISTOGRAM_ENUMERATION("Variations.UniformityTrialGroupNotActive",
value, 4);
}
return false;
}
DCHECK_NE(group_, kNotFinalized);
active_group->trial_name = trial_name_;
active_group->group_name = group_name_;
return true;
}
//------------------------------------------------------------------------------
// FieldTrialList methods and members.
// static
FieldTrialList* FieldTrialList::global_ = NULL;
// static
bool FieldTrialList::used_without_global_ = false;
FieldTrialList::Observer::~Observer() {
}
FieldTrialList::FieldTrialList(
const FieldTrial::EntropyProvider* entropy_provider)
: entropy_provider_(entropy_provider),
observer_list_(new ObserverListThreadSafe<FieldTrialList::Observer>(
ObserverListBase<FieldTrialList::Observer>::NOTIFY_EXISTING_ONLY)) {
DCHECK(!global_);
DCHECK(!used_without_global_);
global_ = this;
Time::Exploded exploded;
Time two_years_from_now =
Time::NowFromSystemTime() + TimeDelta::FromDays(730);
two_years_from_now.LocalExplode(&exploded);
kExpirationYearInFuture = exploded.year;
}
FieldTrialList::~FieldTrialList() {
AutoLock auto_lock(lock_);
while (!registered_.empty()) {
RegistrationList::iterator it = registered_.begin();
it->second->Release();
registered_.erase(it->first);
}
DCHECK_EQ(this, global_);
global_ = NULL;
}
// static
FieldTrial* FieldTrialList::FactoryGetFieldTrial(
const std::string& name,
FieldTrial::Probability total_probability,
const std::string& default_group_name,
const int year,
const int month,
const int day_of_month,
int* default_group_number) {
if (default_group_number)
*default_group_number = FieldTrial::kDefaultGroupNumber;
// Check if the field trial has already been created in some other way.
FieldTrial* existing_trial = Find(name);
if (existing_trial) {
CHECK(existing_trial->forced_);
// If the field trial has already been forced, check whether it was forced
// to the default group. Return the chosen group number, in that case..
if (default_group_number &&
default_group_name == existing_trial->default_group_name()) {
*default_group_number = existing_trial->group();
}
return existing_trial;
}
FieldTrial* field_trial =
new FieldTrial(name, total_probability, default_group_name);
if (GetBuildTime() > CreateTimeFromParams(year, month, day_of_month)) {
// TODO(asvitkine): Temporary histogram. Remove this once it is not needed.
if (name == "UMA-Uniformity-Trial-1-Percent")
UMA_HISTOGRAM_BOOLEAN("Variations.UniformityTrialExpired", true);
field_trial->Disable();
}
FieldTrialList::Register(field_trial);
return field_trial;
}
// static
FieldTrial* FieldTrialList::Find(const std::string& name) {
if (!global_)
return NULL;
AutoLock auto_lock(global_->lock_);
return global_->PreLockedFind(name);
}
// static
int FieldTrialList::FindValue(const std::string& name) {
FieldTrial* field_trial = Find(name);
if (field_trial)
return field_trial->group();
return FieldTrial::kNotFinalized;
}
// static
std::string FieldTrialList::FindFullName(const std::string& name) {
FieldTrial* field_trial = Find(name);
if (field_trial)
return field_trial->group_name();
return "";
}
// static
bool FieldTrialList::TrialExists(const std::string& name) {
return Find(name) != NULL;
}
// static
void FieldTrialList::StatesToString(std::string* output) {
FieldTrial::ActiveGroups active_groups;
GetActiveFieldTrialGroups(&active_groups);
for (FieldTrial::ActiveGroups::const_iterator it = active_groups.begin();
it != active_groups.end(); ++it) {
DCHECK_EQ(std::string::npos,
it->trial_name.find(kPersistentStringSeparator));
DCHECK_EQ(std::string::npos,
it->group_name.find(kPersistentStringSeparator));
output->append(it->trial_name);
output->append(1, kPersistentStringSeparator);
output->append(it->group_name);
output->append(1, kPersistentStringSeparator);
}
}
// static
void FieldTrialList::GetActiveFieldTrialGroups(
FieldTrial::ActiveGroups* active_groups) {
DCHECK(active_groups->empty());
if (!global_)
return;
AutoLock auto_lock(global_->lock_);
for (RegistrationList::iterator it = global_->registered_.begin();
it != global_->registered_.end(); ++it) {
FieldTrial::ActiveGroup active_group;
if (it->second->GetActiveGroup(&active_group))
active_groups->push_back(active_group);
}
}
// static
bool FieldTrialList::CreateTrialsFromString(const std::string& trials_string) {
DCHECK(global_);
if (trials_string.empty() || !global_)
return true;
size_t next_item = 0;
while (next_item < trials_string.length()) {
size_t name_end = trials_string.find(kPersistentStringSeparator, next_item);
if (name_end == trials_string.npos || next_item == name_end)
return false;
size_t group_name_end = trials_string.find(kPersistentStringSeparator,
name_end + 1);
if (group_name_end == trials_string.npos || name_end + 1 == group_name_end)
return false;
std::string name(trials_string, next_item, name_end - next_item);
std::string group_name(trials_string, name_end + 1,
group_name_end - name_end - 1);
next_item = group_name_end + 1;
FieldTrial* trial = CreateFieldTrial(name, group_name);
if (!trial)
return false;
// Call |group()| to mark the trial as "used" and notify observers, if any.
// This is needed to ensure the trial is properly reported in child process
// crash reports.
trial->group();
}
return true;
}
// static
FieldTrial* FieldTrialList::CreateFieldTrial(
const std::string& name,
const std::string& group_name) {
DCHECK(global_);
DCHECK_GE(name.size(), 0u);
DCHECK_GE(group_name.size(), 0u);
if (name.empty() || group_name.empty() || !global_)
return NULL;
FieldTrial* field_trial = FieldTrialList::Find(name);
if (field_trial) {
// In single process mode, or when we force them from the command line,
// we may have already created the field trial.
if (field_trial->group_name_internal() != group_name)
return NULL;
return field_trial;
}
const int kTotalProbability = 100;
field_trial = new FieldTrial(name, kTotalProbability, group_name);
// This is where we may assign a group number different from
// kDefaultGroupNumber to the default group.
field_trial->AppendGroup(group_name, kTotalProbability);
field_trial->forced_ = true;
FieldTrialList::Register(field_trial);
return field_trial;
}
// static
void FieldTrialList::AddObserver(Observer* observer) {
if (!global_)
return;
global_->observer_list_->AddObserver(observer);
}
// static
void FieldTrialList::RemoveObserver(Observer* observer) {
if (!global_)
return;
global_->observer_list_->RemoveObserver(observer);
}
// static
void FieldTrialList::NotifyFieldTrialGroupSelection(FieldTrial* field_trial) {
if (!global_)
return;
{
AutoLock auto_lock(global_->lock_);
if (field_trial->group_reported_)
return;
field_trial->group_reported_ = true;
}
if (!field_trial->enable_field_trial_)
return;
global_->observer_list_->Notify(
&FieldTrialList::Observer::OnFieldTrialGroupFinalized,
field_trial->trial_name(),
field_trial->group_name_internal());
}
// static
size_t FieldTrialList::GetFieldTrialCount() {
if (!global_)
return 0;
AutoLock auto_lock(global_->lock_);
return global_->registered_.size();
}
// static
const FieldTrial::EntropyProvider*
FieldTrialList::GetEntropyProviderForOneTimeRandomization() {
if (!global_) {
used_without_global_ = true;
return NULL;
}
return global_->entropy_provider_.get();
}
FieldTrial* FieldTrialList::PreLockedFind(const std::string& name) {
RegistrationList::iterator it = registered_.find(name);
if (registered_.end() == it)
return NULL;
return it->second;
}
// static
void FieldTrialList::Register(FieldTrial* trial) {
if (!global_) {
used_without_global_ = true;
return;
}
AutoLock auto_lock(global_->lock_);
DCHECK(!global_->PreLockedFind(trial->trial_name()));
trial->AddRef();
global_->registered_[trial->trial_name()] = trial;
}
} // namespace base